Multiple-switchboard apparatus



(No Model.)

7 J. J. GARTY. MULTIPLE SWITGHBOARDAPPARATW.

No. 605,188; Patented Sept. 19, 1893.

UNITED STATES PATENT OFFICE.

JOHN J. CARTY, OF NEWV YORK, N. Y., ASSIGNOR TO THE WESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS.

M u LTIPLE-SWITCHBOARDAPPARATUS.

SPECIFICATION forming part of Letters Patent No. 505,188, datedSeptember 19, 1893. Application filed February 2, 1889. Renewed October16, 1891. Serial No. 408,877. ,(No model.)

To all} whom it may concern.-

Be 1t known that 1, JOHN J. CARTY, a citizen of the United States,residing at New York, 1n the county of New York and State of New York,have invented a certain new and useful Improvement inlVIultiple-Switchboard Telephone-Exchange Apparatus, (Case No. 4,) ofwhlch the following is a full, clear, concise, and exact description,reference being had to the accompanying drawing, forming a part of thlsspecification.

My invention relates to the circuits and other apparatus at the centraloffice of a telephone exchange system in which multiple switch boardsare used. My invention, speaking generally, consists n provldlng meansfor automatically grounding the cut oif portions of the telephone lineswhen the lines are connected together, in connectlon with a source ofcurrent for throwing current upon the telephone lines, this groundconnection being of such lower resistance as compared with theresistance of the operators telephone that, when the telephone isconnected to the cut off portion of any telephone line at the test pieceof a switch included therein, there willbe no appreciable current, and,hence, no sound in the telephone. Heretofore in such systems specialcircuit wires have been employed. Usually each line has been providedwith a special test wire or test circuit. By my invention I dispensewith such test circuits, thereby greatly simplifying the apparatus,while at the same time I provide suitable means for receiving the calls,testing the lines to avoid confusion and makmg the connections anddisconnections.

My invention isillustrated in the accompanying drawing, in whichtelephone line or extends from its station through switches 12 c d, oneswitch on each of the switch boards and thence through the secondary ofan induction coll e and thence through individual annunclator f on thefirst board to ground. Lineg 1s connected in a similar manner throughswitches h 'i la and from the switch It on the last board through thesecondary of induction last board through the secondary of inductioncoil 7" and thence through individual annunciator s to ground. It willbe observed that the switches 19 c, 850., may consist simply of twoinsulated parts, the spring and the frame. As shown at board 1 the plugss s are each provided with two terminals, the tip and the sleeve. Thetips are connected together by strand 8 in the usual manner.

By means of branchess and 8 connection may be made between the tips ofthe plugs and the telephone 8 a switching apparatus 8 being provided forthis purpose in the usual manner. The strand .9 connecting together thesleeves of said plugs s .s is provided with a ground connection 3 Thecord connections are arranged in a similar manner at all the switchboards. As before stated each line is connected through the secondary ofan induction coil as induction coils e Z and r, or other vibratorycurrent inducing device. A rheotome t connected through the primaries ofthese induction coils serves to induce currents of a particularcharacteristic upon each of the lines as long as they remain closed;inserting a plug in the switch of any line cuts off that line from theportion which contains the secondary winding. When a testis made thetone of the rheotome 25 will not be heard in the telephone of theoperator if the line tested is connected or in use at any other board.If the test is made at a board on the line side of the connection it isevident that the test signal cannot be heard since the portion of theline containingthe secondary coil will be entirely out ofi; if, however,the test is made at a board on the ground side of the connection, thatis to say, on the cut off portion of the line, the test signal will notbe heard because the portion of the line tested containing the secondarywinding will be connected directly to ground through the sleeve strandof the cords with which the connection is made at the other board as,for example,

through. sleeve strand 5- and ground connection 3 of the first board.Suppose a signal sent in over line or throwing down shutter f theoperator at the first board seeing shutter f fall will insert plug .9 inswitch I) and throw down the cam lever of switching device :3 so

as to bring the telephone .9 into circuit; she will receive the order attelephone 8 We will say this order is for connection with line g andsuppose line 9 is not connected at either of the other boards, that is,suppose no plug is inserted in either of the spring jack switches z k.The operator at the first board, touching the tip of her plug 8 to theframe of spring ack switch h will get the hum of rheotome t in hertelephone 5 and this will be notice that line 9 is idle; she willtherefore at once insert plug s as shown into switch h, thus'completingthe connection, whereupon she calls up the subscriber of line g With hercalling key in the usual manner. Plugs s and 8 being inserted as shown,the lines a and g are connected through the tips of said plugs and thestrand connecting said tips as before described. The lines a and 9, willbe cut off at switches b and h respectively from induction coils e Z.The portion of the lines thus cut off at the central office will,moreover, be provided with direct ground, connections through thesleeves of the plugs 8 the sleeve strand 3 and the connection .9

We will suppose now that a call is sent over line at throwing downshutter s at the last board. The operator at the last board inserts oneof a pair of plugs in switch q of line at and having received the order,we will say, for line g proceeds to test said line 9. This she does bytouching tip of the other plug of the pair as shown to frame of springjack switch It. Tracing the cut off portion of line g from the centraloffice ground through annunciator m, secondary of induction coil Z,switch and switch 1' to frame of switch h we find, as before stated, adirect ground connection through strand 3 and connection 5*"; therefore,all the current induced on the out off portion of the line through theconverter e will pass to ground and practically no current will be drawnoff through the tip of the plug, applied to switch It, since theresistance of the telephone set will be included in the branch formedfrom the tip of said plug through the operators telephone set at thelast board to ground. Therefore, the operator at the last boardlistening at her telephone will hear no sound and this will be notice toher that the line is busy at some other board. Suppose a similar testwere applied to switch 0 or p when a plug is inserted in switch q asshown. As the secondary of induction coil 1 or other current-inducingdevice, would be cut off from the portion of line at including switches0 p there would, of course, be no vibratory current present at theframes of switches 0 p and no sound would be produced in the telephoneof the operator who should make the test at switch 0 or p on the lineside of the break at switch q.

Having thus described my invention, I claim as new and desire to secureby Letters Patent- 1. The combination with telephone lines, each lineconnected through a different spring j ck switch on each of two or moreswitch boards, and each line being connected through a current inducingdevice to ground, of pairs of loop plugs and cords at the differentboards, the strand of each pair connecting the sleeves of the plugsbeing provided with a ground connection, whereby on connecting any twolines together at one board the portion cut olf from each line will beclosed directly to ground, substantially as and for the purposespecified.

2. Two telephone lines connected together at the central office throughone strand of a pair of cords in combination with the cut off portionsof said lines connected together through another strand of the cords,said strand being connected to ground, whereby the cut off portions ofthe lines are grounded and the talking circuits cut off from the sourceof the test current.

3. Two telephone lines connected together at one of the multiple switchboards of said lines, the cut off portions of said lines which includeeach a vibratory current inducing device being closed through a groundbranch when the lines are thus connected and a branch circuit to groundthrough a telephone at another switch board adapted to be closed to theswitch of either of said lines upon said switch board, whereby it may bedetermmed whether either of said lines is thus connected or in use. I

4. The combination with two telephone lines each extending from groundat the subscribers station thereon to the central oflice and thencenormally each through a different switch on each of two or more switchboards and through an annunciator to ground, of a pair of loopingdevices having two of their terminals connected together while the othercorresponding terminals of the said plugs are connected to ground, saidplugs being adapted to be inserted in switches of said telephone lines,whereby the lines may be looped IIO together for conversation while theportions of said lines cutoff at the switches by the insertion of theplugs are connected to ground,

substantially as and for the purpose specified.

5. The combination with a telephone line, of switches upon the differentboards at the central office, a source of electricity and an annunciatorbetween the last switch and ground, switching apparatus at the diiferentswitch boards, for establishing connection between different lines, andmeans controlled by said switching apparatus adapted to cut off aportion of the line and close the same directly to ground, substantiallyas described.

6. The combination with a telephone line, of switches upon the differentboards at the central office, a source of electricity and an annunciatorbetween the last switch and ground, switching apparatus at the differentswitch boards for establishing connection between dift'erent lines,means controlled by said switching apparatus adapted to cut off aportion of the line and close the same directly to ground, and operatorstesting sets at the different boards provided with connecting apparatusadapted to close the circuit of the telephone at any one of the boardswith the test piece of any switch; whereby on making said test at eitherof said boards the sound will be heard in the telephone, if the linetested is free, while no sound will be produced in the telephone if theline tested is busy,

though the test should be made at the switch included in the out offportion of the line, substantially as described. a

7. The combination with a telephone line, of switches upon the differentboards at the central office, a source of electricity and. anannunciator between the last switch and ground, switching apparatus atthe different switch boards for establishing connection betweendifierent lines, and means controlled by said switching apparatusadapted to cut 0% a portion of the line and close the same to ground,andtelephonic testing apparatus at each board; whereby any line may betested to determine whetherit is in use, substantially as described.

In witness whereof I hereunto subscribe my name this 12th day ofJanuary, A. D. 1889.

JOHN J. CARTY.

W'itnesses:

W. M. RUMBAUGH, O. A. BELL.

